To ask how to report someone smoking weed?

We've got some new neighbours, and we've noticed a smell of weed coming through the wall into our living room. I really hate the smell, and I have a 11 month old who I don't want to be inhaling the smell!

Unless they're operating a cannabis farm or dealing it on a large scale the police really will not be interested or take any action. It would be treated little differently to a complaint about them smoking tobacco tbh.